浑河大桥嵌岩桩水平加载试验研究

以浑河大桥工程为依托,对大桥的试验桩基进行原位水平加载试验,研究了在水平荷载作用下桩顶的荷载-位移曲线、桩身弯矩分布情况等,并通过有限元软件进行数值模拟验证。研究表明:弯矩沿桩身呈抛物线形分布,在距离桩顶4 m左右的位置达到最大值,深度超过8 m以后数值接近于零;受场地环境和嵌岩桩桩形影响,桩顶水平位移和转角均较小,满足容许水平位移的要求;数值模拟与试验结果的曲线变化形式上大体吻合,弯矩和位移的实测值要较模拟值稍低。所采用的试验方法和得到的试验结果将对类似工程试验提供经验和指导。     

The mechanical response of piles with consideration of pile-soil interactions under a periodic wave pressure

The pile-soil interaction under wave loads is an extremely complex and difficult issue in engineering. In this study, a physical model test is designed based on the principle of the gravity similarity to obtain time histories of wave forces of unsteady regular waves, and to measure the magnitude and the distribution of wave forces acting on the piles. A numerical model and relevant numerical methods for the pile-soil contact surface are adopted based on the principles of elastic dynamics. For a practical project, the time histories of wave forces on the piles are obtained through physical model tests. The deformations of the piles in the pile-soil interactions and the distribution of the bending moment on the piles are studied. It is shown that, with the increase of the period of wave pressures, the absolute value of the horizontal displacement of the piles increases, the embedment depth of the piles increases, and the scope of influence of soils increases. The change of the bending moment on the piles is consistent with that of its theoretical results, and the proposed numerical method can very well simulate the properties of the piles.     

装配式快速堵口临时堤坝的稳定性分析

为了研究利用装配式快速堵口装置进行汛期堤坝决口封堵的可行性和有效性,基于CFD软件Fluent建立了堵口装置形成坝体后的三维数值计算模型。通过模型试验验证数值计算方法的可靠性后,计算得到不同工况下水流对坝体的水平作用力和倾覆力矩。计算结果表明:水流力随着决口处流速、决口宽度和深度的增大而增大;堵口装置布置排数的增加也会使水流力略有增大,且这种影响随流速的增大而增大;水流作用引起的倾覆力矩对坝体的稳定性影响很小。     

Combined effects of coastal forest and sea embankment on reducing the washout region of houses in the Great East Japan tsunami

Coastal vegetation is widely recognized for its ability to reduce tsunami damage; however, coastal forests in large areas of the Tohoku and Kanto districts of Japan were destroyed by the Great East Japan tsunami on 11 March 2011. To elucidate the tsunami-mitigating effect of a coastal forest during a destructive tsunami, the combined effects of sea embankment and coastal forest were analyzed using post-tsunami survey data of the damage and a nonlinear long wave equation model that includes the breaking or washout condition of trees. The numerical simulations estimated that a 600-m-long coastal forest reduced the washout region of houses due to a 10-m-high tsunami at the coast by approximately 100 m, and the reduction achieved by a sea wall of approximately 5.4–6.4 m in height was approximately 560–1520 m. The height of a sea embankment or wall with sand dunes greatly affects the breaking condition of trees behind it by changing the tsunami flux overflowing the sea wall and the sand dune. For the combination of a sea embankment and a coastal forest during a destructive tsunami, the tsunami mitigation function of the coastal forest has an optimum value when the fluid force on the trees is strong but not strong enough to break the trees under the condition at which the tsunami overflows the sea embankment. At the investigated site, the effect of the coastal forest was larger than that of the sea embankment under optimal conditions. Thus, a coastal forest on a sand dune should be designed as a mitigation measure behind a sea embankment and optimally designed to protect the houses that are not protected from a tsunami by the sea embankment alone.     

自升式平台踩脚印失稳机理大变形有限元分析

自升式平台桩靴踩脚印失稳相关研究较少,且多为实验研究,土体的流动破坏模式和桩靴失稳机制尚不十分清楚。运用 CEL 有限元方法来模拟桩靴贯入均匀土体的过程,选择出最合适的网格密度,在此基础上模拟桩靴在旧桩坑附近的二次插桩过程,分析了旧桩坑的几何形状（包括深度、坡度和直径）、二次插桩偏心距对桩靴基础二次插桩稳定性的影响规律,考察桩靴的最大峰值水平力 Hmax 、最大峰值弯矩 Mmax ,并联合土体的流动破坏机制分析了桩靴踩脚印失稳机理。     

Z坐标系下分层三维水流数学模型研究

建立了z坐标系下分层三维水流数学模型,避开了在地形突变σ变换下水平压力梯度计算较大的困难.在任意三角形网格中,通过剖开算子法,将方程剖分为不同子算子,用各自适应的数值解法进行求解.潜坝及斜槽水流的计算结果与实验结果吻合较好,而基于σ变换的Delft3D模型计算值与试验值相差较大,因此本文的z坐标分层数学模型可以用来计算包括地形突变的三维水流,并具有较高的精度.     

Modelling and analyzing flow diversion in branching channels with symmetric geometry

This paper aims at the investigation and analysis of numerical and laboratory modelling of flow in branched channels with symmetrical geometry and varying hydraulic conditions. Details of velocity and water‐level profiles in branching locations are discussed. In some low‐slop regions like plains, rivers may be branching; or in alluvial plains where the slop is low, meanders may appear. On the other hand, in the mountainous and semi‐mountainous areas with relatively steep slops, arterial rivers can be formed. Therefore, it is important to learn the behaviour of rivers in branching location and to simulate water flow in branching part of rivers. Details of two‐dimensional numerical model in a main channel and secondary downstream branches are explained and results are analysed and compared against experimental data. With respect to the numerical simulation, velocity and depth in different sections of laboratory model are calculated and the corresponding profiles are developed. The water‐level profiles are calculated and drawn using both the numerical and experimental models. Some long narrow eddies are predicted along internal bank of junction. The comparison of numerical and experimental models proves reasonable results for this research. Copyright © 2010 John Wiley & Sons, Ltd.     

阶梯溢洪道水力特性试验及数值模拟

通过对阶梯溢洪道进行模型试验研究,验证了侧堰的过流能力,研究了典型断面流速、压力及水深在不同工况下的变化规律。试验结果表明:侧堰的过流能力满足设计要求,在各工况下,水深小于边墙设计高度,阶梯段各点空化数小于初生空化数,不会引起空蚀破化。根据原设计方案使用FLUENT对阶梯溢洪道进行数值模拟实验,并将数值模拟计算结果与模型试验结果进行对比分析,发现数值模拟计算结果与物理模型试验结果吻合良好,为深入分析阶梯溢洪道陡坡流场提供可能,同时,为体型结构优化提供技术保障。     

基于有限体积法的三维波生近岸流数值模型

波浪破碎产生近岸流是近岸浅水区域一个重要的水动力现象。该文利用辐射应力的概念,并考虑辐射应力沿水深的变化、波浪破碎引起的水滚以及波流共同作用下的水底剪应力,建立了基于有限体积法的三维波生近岸流数值模型。运用建立的数值模型模拟了两个实验室实验,并同实验的实测结果进行了对比。结果表明,建立的数值模型能够较好地模拟波浪破碎产生的近岸流。     

滑坡堰塞湖溃坝波影响因素分析

滑坡堰塞湖坝体随着上游水位的不断上升极易失稳。基于流体计算软件Fluent,对水体在重力作用下的塌落及演进过程进行数值模拟,分析溃坝洪水在下游河道传播过程中的影响因素,结果表明:上下游水深比、下游河道坡降及弯曲程度均对溃坝洪水的推进速度、波形及流量产生影响。水深比比较小时,下游洪水推进较快;下游河道坡降越大,洪水推进速度越快,流量越大;下游河道弯曲度≥0.25时,溃坝洪水受影响比较明显,波前传播速度减缓,能量耗散增大。     

NUMERICAL SIMULATION OF TRANSIENT FLOW AROUND A SHIP IN UNSTEADY BERTHING MOTION

Ship berthing is a specific maneuver operation. The flow around a berthing ship and the forces acting on the hull are quite different from those for a ship in normal navigation. By solving the unsteady Reynolds-Averaged Navier-Stokes (RANS) equations, the transient flow field around a ship undergoing unsteady lateral motion is simulated and the varying lateral hydrodynamic force acting on the hull is evaluated in this article. The numerical results obtained with different turbulence models are analyzed and compared with experimental results and other numerical results published in literature, and a turbulence model more suitable for simulation of the viscous flow around a ship undergoing unsteady berthing is determined.     

明渠水流泥沙运动水深平均及力矩方程的理论和验证

首次提出了水流泥沙运动水深平均及其力矩方程的概念 ,并从理论上推导出这套方程组。提出水流泥沙运动力矩方程的目的有两个 ,一是在不增加空间维数的情况下可以有效地恢复水流泥沙因子沿水深分布信息 ,克服目前普遍使用的水深平均方程过多地忽略沿水深分布信息的缺点 ;二是增强模型的模拟能力。针对这两个目的是否能真正得到体现 ,分别从理论和实验室资料两个方面对新推导的力矩方程进行了全面的检验。理论验证结果表明 ,一维的力矩方程除了能模拟水深平均的流速和含沙量 ,还能够较好地模拟水流泥沙因子沿水深分布信息 ,这充分说明了一维力矩方程的二维特性。为了检验力矩方程的模拟能力 ,特别选取了一些极端的水流泥沙运动实验 ,如清水冲刷、点源加沙和深槽回淤等。模拟结果表明 ,力矩方程对于这些极端的水沙运动具有较好的模拟能力     

往复流作用下海底管线冲刷模拟研究

海底管线冲刷悬空是诱发管道涡激振动破坏的一个主要原因。为更好地对管线冲刷悬空情况进行评估,本文应用水动力-泥沙冲刷耦合模型,对往复潮流作用淤泥质海床海底管线局部冲刷过程进行了模拟研究,模型采用标准k-ε紊流方程对N-S方程进行封闭,控制方程采用有限差分法进行离散,模拟结果表明,双向潮流作用下,管道局部冲刷轮廓基本呈现对称状态,其最大冲刷深度位置因水流流速的转向而有所摆动,往复流引起的冲刷深度较恒定流情况减小约20%左右。     

Analyses of the stability of submerged ice blocks

This paper proposes the critical conditions for a submerged ice block beneath an intact ice cover to become unstable,as a fundamental component of any numerical model to successfully predict the ice jam formation or the ice jam release events.The flume model experimental and numerical simulation methods are both applied to analyze the stability of submerged ice blocks.The flume model experiment is first conducted,and the experimental results indicate that the influencing factors of the stability of a submerged ice block include the relative length,the relative water depth and the relative width.It was shown that the effect of the relative width on the stability of submerged ice blocks was not well studied.Based on the experimental results,the k-eturbulence model is applied to establish a 3-D numerical model for studying the pressure distribution beneath submerged ice blocks.The effects of the relative width on the Venturi pressure and the leading edge pressure are evaluated.Finally,according to the force balance equation and the moment balance equation,this paper proposes a computational formula for the sliding and underturning critical conditions of submerged ice blocks,and the results are in good agreement with the experimental results.     

上拔力-水平力-扭矩组合荷载作用下斜桩承载特性模型试验

斜桩广泛应用于桥梁、水上钻井平台及风力发电基础等工程中,其承载特性十分复杂。为揭示上拔力-水平力-扭矩共同作用下斜桩单桩的承载特性,利用自主设计制作的加载设备,在砂土地基中开展了4根斜桩室内模型试验,研究了桩身倾角、上拔及水平荷载对受扭斜桩桩顶水平位移、扭转角及桩身扭矩、弯矩的影响。试验结果表明：斜桩水平承载力随桩身倾角的增大而增大;倾角及上拔荷载的增大均会导致斜桩极限扭转承载力的减小;斜桩最大弯矩受到桩身倾斜角度及桩顶上拔荷载的影响,随其增加而增加;组合荷载作用下的斜桩存在有效荷载传递深度。     

Wave-current impacts on surface-piercing structure based on a fully nonlinear numerical tank

Fully nonlinear wave-body interactions for a surface-piercing structure with combined wave-current flow in different water depths are studied by using a 2-D numerical tank. The model is based on Reynolds averaged Navier-Stokes(RANS) equations and renormalization group(RNG) k- model. The mean and maximum wave-current impacts, including forces in two directions and rotational moment, are calculated and discussed. The effects of U/ C and water depth condition on forces and moment have been investigated and the results for combined irregular waves and currents are compared with those induced by combined regular waves and currents.     

堤防决口封堵的水力学特性

堤防决口抢险需以水流水力学特性为依据,封堵方法亦直接影响其封堵效率。首先对决口水流遇障碍物的洪水演进过程进行模拟,将水深计算结果与Biscarini等的试验数据进行对比,结果吻合较好,验证了数值模型的可靠性、准确性。以上饶市某一河道为例,基于FLOW-3D软件建立了堤防决口水流模拟的三维数值模型,对立堵法、平堵法封堵决口进行数值模拟,得到封堵过程中决口附近水位场和流速场分布规律。数值模拟结果显示:该堤防决口进口附近立堵法、平堵法块石前水位壅高明显,流速增大,最大水深分布在决口靠右位置,最大流速分布在决口靠左位置。根据决口附近流速分布规律,封堵时建议先对左侧决口堤脚进行裹头处理,而后可考虑采用大粒径块石单体抛投以降低流速,再采取群体抛投方式进占合龙。所用模拟方法和数值模型可为堤防抢险及制定堤防决口封堵方案提供参考。     

Development of a quasi-3d numerical model for sediment transport prediction in the coastal region

To predict sediment transport in the coastal environment is of particularly importance for coastal and environmental engineers. The conventional 2DH computer models have certain limitation for their application in the complex flows. To describe details of flow structure across the water column and intra-wave processes, which are crucial for sand transport calculation, the present paper discussed implementation and validation of an intra-wave sand transport model with an existing phase resolving wave-current model. Model formulation and assumptions are presented briefly with details of model testing on several existing laboratory experiments. The model-data comparison indicates the ability of the numerical model system for sand transport prediction in a prototype scale. Further model validation and testing on field measurements are also needed.     

潜体在两层海内波中的波浪力计算

本文以近似潜艇的细长回转体为模型，在两层海模式中三种不同潜深下，利用边界元法计算了内波对潜体的一阶垂荡波浪力和一阶纵摇波浪力矩，作为特例计算了近水面潜体的波浪力及力矩，并与实验结果进行了比较，两者吻合较好。